An “image display device” employing a planar image-forming optical element (microlens array) has been proposed as a means for displaying a two-dimensional image such as a photograph as a pseudo-three-dimensional image in a manner floating up in space by means of a relatively simple configuration (with reference to Patent Literature 1 and the like, for example).
This image display device is provided with a pair of microlens arrays (image-forming optical element) positioned in a parallel spaced-apart relation to an image display surface such as an LCD and including a plurality of convex lenses (unit optical elements) disposed adjacent to each other in a matrix on opposite surfaces. Using the image-forming function of the microlens arrays, the image display device is adapted to form an erect image of unity magnification corresponding to the aforementioned two-dimensional image in a space opposite from the aforementioned image display surface (in a position opposite from the image display surface with respect to an element surface of the aforementioned image-forming optical element).
However, the aforementioned formed image (spatial image) is projected directly in front of the microlens arrays in the aforementioned image display device. For appropriate viewing of this spatial image, it is necessary to arrange a viewer, the microlens arrays and the image display surface in a straight line. This results in a problem such that a viewable viewing angle is narrow. Also, the aforementioned image display device, which requires large space on a rear side as viewed from the viewer, is low in flexibility of installation, and imposes on the viewer such an inconvenience that the viewer must look into the arrays from a specific position in front of the aforementioned microlens arrays to view the image.
On the other hand, the present applicant proposes a display device which comprises a flat panel display such as an LCD, and a planar image-forming optical element (a micromirror array, with reference to Patent Literature 2) including a multiplicity of recessed unit optical elements or protruding unit optical elements arranged in an array and each having two mirror surfaces (corner reflectors) orthogonal to each other in Japanese Patent Application No. 2012-81248 and in Japanese Patent Application No. 2012-185198. As shown in FIG. 8, this display device is configured such that the flat panel display D is disposed on one surface side of (under) the image-forming optical element, with a display surface Da of the flat panel display D inclined at a predetermined angle α (not less than 30° and less than 90°) with respect to an element surface P of the aforementioned image-forming optical element (micromirror array M). Thus, the aforementioned display device is capable of sharply displaying a spatial image standing up obliquely toward the front side (viewer side) in space over the device in a manner floating up from the upper surface of the aforementioned image-forming optical element. Also, this display device has characteristics of being able to be configured as a compact device, being high in flexibility of arrangement, and being excellent in portability.